A STATCOM arrangement (10) comprises a STATCOM (1) configured to be connected to a three-phase AC grid (11). The STATCOM comprises a plurality of converter arms (3), each converter arm comprising a plurality of series connected converter cells (5). The STATCOM arrangement also comprises an Energy Storage System, ESS, (20) comprising an energy storage, ES, (21) and energy storage switches (SES) for connecting the ES to the grid (11) via the converter arms. The plurality of converter arms comprises a plurality of intermittently usable chain-links of the series connected converter cells. Each of said chain-links is used for STATCOM operation during a part of a fundamental operation cycle of the STATCOM. The energy storage switches connect the ES to at any point in time via one of said chain- links which is not used for the STATCOM operation at said time point.
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